How to calculate values on Hierarchy node level in WEBI

Hi Experts

I have a BI Query ,which have GL account Hierarchy(FSV) Drill down like

Revenue 213.15

Operating Expense 28.49

Revenue and Operating Expense are two node of the hierarchy ,similarly under these sub node and GL grouping is done in FSV(Hierarchy).

I need to calculate Operating Expenses % and report look like

Revenue 213.15

Operating Expense 28.49

Operating Expenses % 13%

i.e Operating Expences % = Operating Expences / Revenue *100

how It will done in Webi rich Client.

Regards

Abhi